1. Field of the invention.
This invention relates to mechanisms for automatically interrupting the electrical heating circuit of a kiln; and, specifically, to an alarm device for signaling when such interruption has taken place.
2. Description of the prior art.
Kilns are used by ceramic artists and hobbyists for the firing of ceramic products. Various automatic control systems for turning off the kilns are known. A mechanism for automatically interrupting the electrical heating circuit of a kiln after the interior of the kiln has been exposed to a predetermined amount of heating is disclosed in U.S. Pat. Nos. 2,675,600 and 3,287,530 issued to W. P. Dawson. The mechanism disclosed employs a mechanical system of rods, levers, switches, and a heat sensitive element for initiating the movement of the various elements comprising the system when heating is finished. In particular, one of the elements is a pivoted weight which rotates downward when an upper portion of the weight is released by a lever. The downward rotation of the weight actuates a switch which turns off the electrical supply to the kiln. Turning off the electrical supply shuts off the heat source to the kiln.
However, the kiln operator may make many unnecessary trips to visually check to determine whether he kiln has shut off. Knowing whether a kiln has shut off is important to prevent the possibility of inadvertant overfiring due to an equipment malfunction and as a tool for choosing proper firing time. If the length of the firing is known, the fired product can be examined to see if in the future a shorter or longer firing time is desired. Additionally, the kiln operator may not be aware that the cooldown period has started and thus prolong the cooldown period longer than necessary. During such unnecessary extension of the cooldown period, the kiln, and the investment in the kiln, is not being utilized. Firings of ceramic products which could take place do not take place.